Definitely overreacting
If you had mistaken black malt for the crystal, then yeah you would be way off base.. but crystal 120 for 80 is not that big of a deal..
The 120 has more of a burnt sugar character than caramel character, but really, it will be totally fine.. The 120 is not 'sweeter' than the 80, so it will not upset your balance..
Keep the dry-hop according to the recipe and let us know how it ends up tasting..